Glass containers are typically formed by forcing gas into the interior of a parison of semimolten glass in a mold. The glass parison expands against the interior surfaces of the mold to form a bottom and a sidewall with an annular rim defining an opening of the container. During the forming process, various types of defects may be formed, some of which require the container to be rejected. Defects known as split seams and vertical checks may be present in the sidewall of the container and may extend through the entire thickness of the sidewall so that it weakens the container to the extent that it may leak or even shatter during filling, sealing or subsequent handling. Split seams and vertical checks are mirror-like or reflective cracks that lie in a longitudinal plane parallel to the longitudinal axis of the container and extend generally radially from the longitudinal axis of the container. For convenience, the split seam defect and the vertical check defect will be referred to generically as radial reflective defects.
An inspection device for detecting a radial reflective defect or crizzle is disclosed in U.S. Pat. No. 3,171,033 to B. B. Mathias et al and assigned to the assignee of the present invention. In this inspection device, a beam of radiant energy which can be transmitted through the material of the container is focused on a singular spot on the interior wall of the rim of the container at an acute angle to a radial plane. A radial reflective defect will cause a portion of the beam to be reflected by the reflective surface of the defect while the other portion of the beam is refracted. An element sensitive to the radiant energy of the beam is positioned with its line of vision forming an angle of 75 degrees to 105 degrees with the direction of the beam toward the rim so that the sensitive element will become energized by the passage of a radial reflective defect into the path of the singular spot of the beam. Means are provided in the line of vision of the sensitive element for focusing the portion of the beam directed into the element in a plane adjacent the element. When the sensitive element becomes energized, it provides a signal which actuates a mechanism to reject the container. The major problem unsolved by this previous invention relates to the limitations associated with using a single spot illumination to detect radial reflective defects. The single spot illuminates only the rim portion of the container and therefore is capable of detecting only those radial defects in the rim. However, radial defects may be formed anywhere along the sidewall of the container. U.S. Pat. No. 4,171,481 granted Oct. 16, 1979, to Y. M. Mima et al, discloses an inspection device which also employs a beam of radiant energy, but which also comprises a multisurface rotary mirror which reflects the beam to longitudinally scan the sidewall of the container as it rotates. The device also comprises a pair of eliptical cylindrical mirrors to gather and focus the light on an array of photoelectric elements. Although this device does scan the sidewall of the container, the mirrors required to implement the scanning are complex in shape and difficult to maintain in a dirty operational environment.